1. Field of the Invention
The present invention relates to a method and an apparatus for thermal printing on a printing target such as a cardboard, wood, concrete, or steel sheet constituting a part of a box or a container.
2. Description of the Background Art
In general, as a method of printing a limited number of patterns onto a large number of printing targets, there has been a method using a stamp printer.
However, in such a conventional method using a stamp printer, there arises a need to temporarily stop the printing process in order to manually change the stamp in accordance with the desired printing patterns, so that the work required for operating a conventional stamp printer can be quite tedious as well as inefficient. In addition, in order to operate such a conventional stamp printer, there is also a need to secure a rather large storage space for stocking a large number of different stamps to be used in the stamp printer, so that the conventional method using a stamp printer has also been ineconomical in that respect.
Moreover, in such a conventional method using a stamp printer, there is a need to make test printings for at least several times, every time the stamp is changed to a new one, in order to secure a uniform spread of the ink on the stamp as well as for adjusting a positioning of the stamp, so that the conventional method using a stamp printer has been ineconomical in that respect as well.
On the other hand, conventionally, a thermal printing has been utilized in printing on a relatively small printing target, in which the printing is achieved by placing a carbon ribbon over a printing surface and moving a printing head over the carbon ribbon to thermally print desired patterns on the printing surface.
However, such a conventional method of thermal printing is known to be associated with the following drawbacks, which have severely limited a practical implementation of an apparatus for thermal printing as well as its range of applicability.
First of all, in the conventional thermal printing, both the imprinting on the carbon ribbon as well as the transfer of the imprinted printing pattern are carried out at the same printing position, it has been difficult to apply such a conventional thermal printing to a printing of diverse patterns such as a printing of bar codes, on variety of not necessarily sufficiently flat printing surface such as that of a cardboard, wood, concrete, or steel sheet.
Secondly, in a conventional thermal printing apparatus, it has been structurally impossible to print patterns with a part of patterns left blank, where the blank part is to be printed at later time by a separate means such as a handy type printer for example.
Thirdly, in a conventional apparatus for thermal printing, both the imprinting of patterns on the carbon ribbon by the printing head and the thermal transfer of the patterns from the carbon ribbon to the printing surface take place at the same printing position, so that a stability of the printing head with respect to the printing surface is a crucial factor for the realization of a high precision printing. However, in a case of printing such printing target as a cardboard, the printing head has conventionally been supported by a bridge structure bridging over the printing surface, but such a bridge structure is known to be not stable enough to obtain a sufficient stability for the realization of the high precision thermal printing of patterns such as bar codes which require a very high level of precision.